Fixes #3270

src/Util/EsmResolver.js

@@ -0,0 +1,49 @@
+import debugUtil from "debug";
+
+const debug = debugUtil("Eleventy:EsmResolver");
+
+let lastModifiedPaths = new Map();
+export async function initialize({ port }) {
+	// From `eleventy.importCacheReset` event in Require.js
+	port.on("message", ({ path, newDate }) => {
+		lastModifiedPaths.set(path, newDate);
+	});
+}
+
+// Fixes issue https://github.com/11ty/eleventy/issues/3270
+// Docs: https://nodejs.org/docs/latest/api/module.html#resolvespecifier-context-nextresolve
+export async function resolve(specifier, context, nextResolve) {
+	try {
+		// Not a relative import and not a file import
+		// Or from node_modules (perhaps better to check if the specifier is in the project directory instead)
+		if (
+			(!specifier.startsWith("./") && !specifier.startsWith("file:")) ||
+			context.parentURL.includes("/node_modules/")
+		) {
+			return nextResolve(specifier);
+		}
+
+		let fileUrl = new URL(specifier, context.parentURL);
+		if (fileUrl.searchParams.has("_cache_bust")) {
+			// already is cache busted outside resolver (wider compat, url was changed prior to import, probably in Require.js)
+			return nextResolve(specifier);
+		}
+
+		let absolutePath = fileUrl.pathname;
+		// Bust the import cache if this is a recently modified file
+		if (lastModifiedPaths.has(absolutePath)) {
+			fileUrl.search = ""; // delete existing searchparams
+			fileUrl.searchParams.set("_cache_bust", lastModifiedPaths.get(absolutePath));
+			debug("Cache busting %o to %o", specifier, fileUrl.toString());
+
+			return nextResolve(fileUrl.toString());
+		}
+	} catch (e) {
+		debug("EsmResolver Error parsing specifier (%o): %o", specifier, e);
+	}
+
+	return nextResolve(specifier);
+}
+
+// export async function load(url, context, nextLoad) {
+// }

src/Util/Require.js

@@ -1,14 +1,29 @@
 import fs from "node:fs";
 import path from "node:path";
 import { fileURLToPath } from "node:url";
-import { createRequire } from "node:module";
+import module from "node:module";
+import { MessageChannel } from "node:worker_threads";
 
 import { TemplatePath } from "@11ty/eleventy-utils";
 
 import eventBus from "../EventBus.js";
 
+const { port1, port2 } = new MessageChannel();
+
+// ESM Cache Buster is an enhancement that works in Node 18.19+
+// https://nodejs.org/docs/latest/api/module.html#moduleregisterspecifier-parenturl-options
+// Fixes https://github.com/11ty/eleventy/issues/3270
+if ("register" in module) {
+	module.register("./EsmResolver.js", import.meta.url, {
+		data: {
+			port: port2,
+		},
+		transferList: [port2],
+	});
+}
+
 // important to clear the require.cache in CJS projects
-const require = createRequire(import.meta.url);
+const require = module.createRequire(import.meta.url);
 
 // Used for JSON imports, suffering from Node warning that import assertions experimental but also
 // throwing an error if you try to import() a JSON file without an import assertion.
@@ -37,7 +52,13 @@ let lastModifiedPaths = new Map();
 eventBus.on("eleventy.importCacheReset", (fileQueue) => {
 	for (let filePath of fileQueue) {
 		let absolutePath = TemplatePath.absolutePath(filePath);
-		lastModifiedPaths.set(absolutePath, Date.now());
+		let newDate = Date.now();
+		lastModifiedPaths.set(absolutePath, newDate);
+
+		// post to EsmResolver worker thread
+		if (port1) {
+			port1.postMessage({ path: absolutePath, newDate });
+		}
 
 		// ESM Eleventy when using `import()` on a CJS project file still adds to require.cache
 		if (absolutePath in (require?.cache || {})) {